It drives up the cost of living for regular people because of higher real estate prices in big cities (due to limited space).
This benefits the rich (landlords and big company shareholders) and drains resources away from smaller suburbs and less wealthy citizens who are forced to move to big cities to find jobs.
I think in this case he's including the suburbs in urban, as contrasted with rural living. In that light urbanization is generally harmful, as rural living tends to have less of an effect on wildlife since individuals are rarely stopping foxes, deer, etc from crossing through their property in the same way that miles of sprawl and deforested lawns do.